In the manufacture of ammunition cartridges, it is necessary to heat the cartridges to a hardening temperature and then quench harden the cartridges. Thereafter the cartridges are tempered to the desired hardness. A variety of apparatus has been developed for this purpose. Generally, the cartridges are heated in a gas fired furnace. Thereafter they are removed and quench hardened in a tank. From the tank, the workpieces are again heated to a tempering or annealing temperature. This type of procedure requires a substantial amount of handling and reorientation of the cartridges between the three basic processing steps. As is well known, induction heating is considered a more acceptable form of heating when applicable. Thus, attempts have been made to inductively heat the cartridges by using multiturn coils. A cartridge is first placed in the coil and heated inductively. Then the cartridge is removed for quench hardening. This process is not efficient because the cartridge must be heated from ambient temperature to the hardening temperature in a single induction heating coil. To overcome this problem, other similar workpieces have been heated by a series of axially aligned multiturn coils. The workpiece is progressively neated as it is progressively moved through the individual coils. In this manner, each coil performs a certain amount of the heating operation on the progressively moving workpieces. In some prior induction heating units, the workpieces are in abutting relationship and periodically advanced through successive multiturn coils. These processes cannot be used effectively for cartridges since the cartridges are often made of a material which can be marked and defaced by sliding along rails through the axially aligned multiturn coils. Also, abutment of cartridges can cause damage at the ends, as well as possible uneven heating. There are spaces between successive coils in which there is no heating effect; therefore, fluctuations in the heated temperature of the workpieces can occur between two adjacent coils.